Another package arrived: this time some chrome vent rings from ChromDesign. Installation didn't take more than a minute: the rings themselves are self-adhesive, and the packaging even included a small pad soaked in alcohol to remove any grease from the plastic that would hinder the adhesion. Once fitted, they really liven up the interior. I think the 2004 model Miatas even have them stock. Oh, and one more thing: if you buy these vent rings, you absolutely have to buy the hazard switch surround as well.
Yes, I know, the dash is full of dust.
Greets to Kizome for pointing out how this photo looks like a robot face from a '70s kids' cartoon ;)